JP2010197223A - Wattmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily measure power regardless of the kind of an electric path to be measured. <P>SOLUTION: A processing part executes kind setting processing (step 65) wherein, when a set button disposed on a setting part is operated, a channel whose set kind is an AC electric path (a single-phase three-wire system electric path, a three-phase three-wire system electric path and a three-phase four-wire system electric path) is set for AC use, and a channel whose set kind is a single-phase two-wire system electric path is set for AC use or for DC use corresponding to the kind of a line voltage inputted into the channel, and executes synchronous integration setting processing (step 66) wherein a channel set for AC use in the kind setting processing is set to calculate power synchronously with a zero cross point of a line voltage inputted into the channel, and a channel set for DC use in the kind setting processing is set to calculate power by DC integration in each prescribed time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention has a plurality of channels to which a current detection probe and a voltage detection probe are connected (one for each), and calculates and displays the power of a circuit to be measured to which the current detection probe and the voltage detection probe are connected. It is related to the wattmeter.

  As this type of wattmeter, the present applicant has already proposed a wattmeter (power meter) disclosed in Patent Document 1 below. This wattmeter measures AC voltage and AC current, and includes an input unit, a setting unit, a CPU, ROM and RAM as storage means, and a display unit. In this case, the input unit includes a plurality of channels to which one current detection probe and one voltage detection probe are connected, and an A / D converter that converts an alternating current and an alternating voltage input from each channel into digital signals. It has. In this wattmeter, when measuring the power of the circuit to be measured, the type of the circuit to be measured (single-phase 2-wire, single-phase 3-wire, three-phase 3-wire or three-phase 4-wire power transmission method) is set by the operator. Set to Further, a measurement range or the like that determines an appropriate voltage range or current range is selected according to the AC voltage or AC current value to be measured.

JP 2000-258484 A (page 3, FIG. 1)

  However, the above wattmeter has the following problems to be solved. That is, when the type of circuit to be measured is any one of a single-phase three-wire circuit, a three-phase three-wire circuit, and a three-phase four-wire circuit, the line current and the line voltage of these circuits are always alternating current. The power can be measured with the above-mentioned wattmeter. However, when the type of electric circuit to be measured is a single-phase two-wire electric circuit, there are cases where the line current and line voltage of this electric circuit are alternating current and direct current. In this case, since the content of the integrated power calculation process differs between AC and DC, the above power meter cannot accurately measure the integrated power value when the type of circuit to be measured is a single-phase two-wire circuit. There is a problem to be solved. In addition, as a method for solving this problem, it is conceivable that the type of line current and line voltage to be input (whether AC is DC) can be set for each channel. For channels set in a single-phase two-wire circuit, it is necessary to determine whether the voltage is AC or DC by observing the waveform of the line voltage or line current, creating a new problem that complicates the power measurement procedure. To do.

  The present invention has been made to solve such a problem, and a main object of the present invention is to provide a power meter that can easily measure the power value regardless of the type of the circuit under test.

  In order to achieve the above object, the power meter according to claim 1 includes a set of a current detection terminal and a voltage detection terminal configured to be able to input the line current and the line voltage of the circuit to be measured one channel at a time. An input unit that samples the line current and the line voltage input from each channel, converts them to current data and voltage data, and outputs them; and the type of the circuit to be measured connected to each channel A setting unit that sets the power for each channel, and a processing unit that executes a power calculation process for calculating power for each channel based on the current data and the voltage data of each channel output from the input unit. The setting unit is provided with a setting button, and the processing unit is configured such that when the setting button is operated, The channel whose set type is an AC circuit is set for AC and the line voltage input to the channel is set for the channel whose set type is a single-phase two-wire circuit. The type setting process for setting to AC or DC depending on the type of the channel, and the channel set for AC in the type setting process is synchronized with the zero cross point of the line voltage input to the channel. A setting for calculating the power and a synchronous integration setting process for setting the power to be calculated by DC integration every predetermined time for the channel set for DC in the type setting process are executed.

  The power meter according to claim 2 is the power meter according to claim 1, wherein the processing unit calculates a harmonic component for each channel based on the current data and the voltage data of each channel. A wave component calculation process is configured to be executable, and when the setting button is operated, for the channel set for AC in the type setting process, the zero-crossing point of the line voltage input to the channel And a harmonic setting process for setting the harmonic component to be calculated every predetermined time for the channel set for DC in the type setting process. Execute.

  According to the power meter of the first aspect, by operating the setting button provided in the setting unit, the processing unit determines the type of line voltage (in the internal items necessary for calculating the power in each channel ( It is possible to automatically set the setting contents while automatically determining whether it is AC or DC), which is incorrect compared to a configuration in which multiple internal items required for power calculation are set manually. The setting can be completed very easily while avoiding the setting. Therefore, according to this wattmeter, it is possible to easily and automatically measure the power for the measured circuit regardless of the type of the line voltage, that is, regardless of the type of the measured circuit.

  According to the wattmeter described in claim 2, since a plurality of internal items necessary for the calculation of the harmonic component are automatically set by the operation of the setting button, it is extremely easy to avoid erroneous setting. Settings necessary for calculating the harmonic component can be completed. Therefore, according to this power meter, it is possible to automatically and easily measure the harmonic component of the measured circuit in a short time regardless of the type of the line voltage, that is, regardless of the type of the measured circuit. .

2 is a block diagram showing a configuration of a wattmeter 1. FIG. 4 is a flowchart for explaining an operation of measurement processing by the wattmeter 1; 3 is a flowchart for explaining an operation of a simple setting process in the measurement process of FIG. 2. 3 is a flowchart for explaining an operation of a type setting process in the measurement process of FIG. 2. 3 is a flowchart for explaining an operation of a synchronous integration setting process in the measurement process of FIG. 2. 3 is a flowchart for explaining the operation of harmonic setting processing in the measurement processing of FIG. 2.

  Hereinafter, with reference to an accompanying drawing, the form of the wattmeter concerning the present invention is explained.

  First, the configuration of the wattmeter 1 will be described with reference to the drawings.

  As shown in FIG. 1, the wattmeter 1 includes an input unit 2, a processing unit 3, a storage unit 4, a setting unit 5, and a display unit 6, and is configured to be able to measure the power of the circuit under measurement. The input unit 2 includes a set of current detection terminals and voltage detection terminals, which will be described later, configured to be able to input the line current I and the line voltage U of the circuit to be measured for each channel, and for each channel. An amplifier that amplifies the AC signal input through the current detection terminal and the voltage detection terminal at a magnification corresponding to the range set for each channel, and samples the AC signal amplified by the amplifier at a predetermined sampling period. It comprises an A / D converter (not shown) that converts it into digital data and outputs it. The input unit 2 is configured so that a current detection probe can be connected to the current detection terminal of each channel, and a voltage detection probe can be connected to the voltage detection terminal. In this case, the current detection probe converts the detected line current into an AC voltage whose amplitude changes according to the current value and outputs the AC voltage. For this reason, the signal input to each current detection terminal via the current detection probe is an AC voltage, and this AC voltage indicates the line current detected by the current detection probe as described above. In order to facilitate the understanding of the invention, the signal input to each current detection terminal will be described as a line current I. The range of each channel is individually set by a range switching control signal S1 output from the processing unit 3.

  In this example, as an example, the input unit 2 includes four channels of sets of two current detection terminals to which a current detection probe is connected and two voltage detection terminals to which a voltage detection probe is connected. As shown in FIG. 4, the line current I1 and the line voltage U1 are input for each channel from the set of the current detection terminal 11 and the voltage detection terminal 12 in the first channel CH1, and the current detection terminal 13 and the voltage detection in the second channel CH2 are input. The line current I2 and the line voltage U2 are input for each channel from the set of the terminals 14, and the line current I3 and the line voltage U3 are set for one channel from the set of the current detection terminal 15 and the voltage detection terminal 16 in the third channel CH3. Line current I4 and line voltage from the set of current detection terminal 17 and voltage detection terminal 18 in the fourth channel CH4. 4 and it can be input configured one channel minute. The line currents I1, I2, I3, and I4 are also referred to as “line current I” unless otherwise distinguished, and the line voltages U1, U2, U3, and U4 are also referred to as “line voltage U” unless otherwise distinguished. Say.

  With the above configuration, the input unit 2 has the line current I input to the current detection terminal of each channel via the current detection probe and the line voltage input to the voltage detection terminal of each channel via the voltage detection probe. U is amplified at a magnification corresponding to the range in the amplifier, and converted into digital data (current data Di for the line current I and voltage data Du for the line voltage U) by the A / D converter, The digital data of which channel is output in a state where it can be identified.

  The processing unit 3 is composed of a CPU, and stores the current data Di and the voltage data Du output from the input unit 2 into the storage unit 4 according to an operation program stored in the storage unit 4, and each channel CH1. ~ CH4 (also referred to as “channel CH” unless otherwise specified) Storage processing for storing the type of circuit under measurement to be stored in the storage unit 4, and internal settings that need to be set when calculating power and calculating harmonic components Internal item setting processing for setting the content of the item, power calculation processing for calculating power based on the current data Di and voltage data Du output from the input unit 2, and harmonics based on the current data Di and voltage data Du Harmonic component calculation processing for calculating components is executed. The storage unit 4 includes a semiconductor memory such as a ROM and a RAM, and stores an operation program for the processing unit 3 in advance and functions as a work memory for the processing unit 3.

  The setting unit 5 includes an operation panel as an example, and includes a selection button for selecting (setting) the type of the circuit under measurement to be measured in each channel CH. In addition, the setting unit 5 selects the type of electric circuit to be measured selected by the selection button, that is, the connection form of the electric circuit (for example, a single-phase two-wire electric circuit, a three-phase three-wire electric circuit, and a three-phase four-wire electric circuit). Connection data D <b> 1 shown is output to the processing unit 3. The setting unit 5 is provided with various setting buttons. The setting unit 5 sets the AC / DC of the signal to be measured in each channel (setting each channel to be used for AC or DC. In other words, each Setting the signal type (AC or DC) in the measured circuit to be measured in the channel), setting the measurement lower limit frequency of the signal to be measured in each channel, setting the range of each channel, and setting the synchronization for calculating the power of each channel Manual setting of power calculation method (AC integration method or DC integration method) for each channel, rectification method setting for each channel, and synchronization setting for measuring harmonic components and other internal items ). Further, the setting unit 5 includes a simple setting button 5a that is a setting button for causing the processing unit 3 to execute a simple setting process, and a calculation start button (not illustrated) that is a setting button for starting the power calculation process. )). In addition, the setting unit 5 includes operation data D2 including data specifying the setting contents of each internal item and data specifying each of the operation on the simple setting button 5a and the operation on the calculation start button. Output to the processing unit 3. The display unit 6 includes a display device such as an LCD (Liquid Crystal Display), and displays calculated values such as power and harmonic components under the control of the processing unit 3.

  Next, the operation method together with the operation of the wattmeter 1 will be described. A current detection probe 21 is connected in advance to each of the current detection terminals 11, 13, 15, and 17 constituting each channel CH1 to CH4 of the input unit 2, and a voltage is connected to each of the voltage detection terminals 12, 14, 16, and 18. It is assumed that the detection probe 31 is connected in advance.

  First, the operator operates the selection button of the setting unit 5 to select (set) the type of electric circuit to be measured to be measured in each channel CH. In this case, the setting unit 5 outputs connection data D1 indicating the type of the electric circuit to be measured to the processing unit 3. When the connection data D <b> 1 is output from the setting unit 5, the processing unit 3 performs a storage process of inputting the connection data D <b> 1 and storing it in the storage unit 4. Next, the operator connects the current detection probe 21 and the voltage detection probe 31 of each channel CH to the corresponding electric circuit to be measured. In this state, in the wattmeter 1, the input unit 2 converts the line current I input from the current detection terminals 11, 13, 15, and 17 in the channels CH <b> 1 to CH <b> 4 into current data Di, and outputs the current data Di. The line voltage U input from each voltage detection terminal 12, 14, 16, 18 is converted into voltage data Du and output. As an example, the amplifier of each channel CH of the input unit 2 starts an amplification operation at a magnification (minimum magnification) corresponding to the maximum range at the start of operation.

  After storing the connection data D1 in the storage unit 4, the processing unit 3 starts the storage process of the current data Di and the voltage data Du in the storage unit 4, and also starts the measurement process 50 shown in FIG. In the measurement process 50, the processing unit 3 first executes an internal item setting process (step 51). In this internal item setting process, the processing unit 3 executes the setting of each internal item described above that is necessary for power calculation and harmonic component calculation. Specifically, when the presence or absence of input of the operation data D2 specifying the operation on the simple setting button 5a from the setting unit 5 is detected and the input of the operation data D2 specifying the operation on the simple setting button 5a is detected, A simple setting process 60 shown in FIG. 3 is executed to set internal items. On the other hand, when the input of the operation data D2 including data on the internal item set manually is detected, each internal item is set according to the setting content specified by this data.

  The simple setting process 60 will be described in detail with reference to FIGS. 3 to 6. In the simple setting process 60, the processing unit 3 first sets the measurement lower limit frequency to the wattmeter 1 as shown in FIG. Is set to the minimum value in the input rated frequency range (step 61). This wattmeter 1 has not only a line current I and line voltage U at a commercial frequency (50 Hz or 60 Hz) but also a line current I and a line at a frequency within an input rated frequency range (for example, 10 Hz to 5 kHz) including the commercial frequency. The power and harmonic components of the inter-voltage U can be measured. For this reason, in the simple setting process 60, the minimum value (0.5 Hz) of the input rated frequency range of the wattmeter 1 is set to the measurement lower limit so that the frequency of the line current I and the line voltage U allowing measurement is the widest. Set as frequency.

  Next, the processing unit 3 outputs a control signal S1 to the input unit 2 while controlling the gain of the amplifier of each channel CH in the input unit 2 while discriminating the values of the current data Di and the voltage data Du. The automatic range control to be automatically executed is set (step 62). When this control is set manually, an arbitrary range is selected from a plurality of ranges (a plurality of current ranges for the line current I and a plurality of voltage ranges for the line voltage U) for each channel CH. It is possible to select and set fixedly. However, since the levels of the line current I and the line voltage U are unvalued, the simple setting is automatically set so that any level of the line current I and the line voltage U can be measured in a range with no excess or deficiency. Set to range control. Subsequently, the processing unit 3 sets, as the line voltage U, a signal (hereinafter also referred to as “original signal”) from which the synchronization necessary for calculating the power for each channel CH is extracted (step 63). ). According to the manual setting, the line current I or the line voltage U can be set as the original signal for each channel CH. However, since the line voltage U is generally used as the synchronization original signal, the simple setting is possible. Then, this line voltage U is set to the original signal. Further, the processing unit 3 sets the rectification method for the line current I and the line voltage U in each channel CH to RMS (step 64). According to the manual setting, each channel CH can be set to either a rectification method of RMS (Root Mean Square) rectification or Mean (average value) rectification, but is generally set to RMS. Therefore, the simple setting is set to RMS.

  Next, the processing unit 3 executes a type setting process 65 for setting the type of signal for the connected circuit under measurement for each channel CH (step 65). In this type setting process 65, as shown in FIG. 4, the processing unit 3 first determines whether or not the channel CH is set to be connected to the single-phase two-wire electric circuit (step 71). When not set to a single-phase two-wire circuit, that is, when set to any of a single-phase three-wire circuit, a three-phase three-wire circuit, and a three-phase four-wire circuit, this channel CH Since the input line current I and the line voltage U are always AC, this channel CH is set for AC and the fact is stored in the storage unit 4 (step 72).

  On the other hand, when it is determined in step 71 that the channel CH is set to the single-phase two-wire electric circuit, the processing unit 3 determines the line voltage U measured in the channel CH stored in the storage unit 4. Of the line voltage U, the average value of the DC component of the line voltage U, the average value of the AC component (specifically, the average value of the effective values after rectification of the AC component described above), the maximum value, and A minimum value is calculated (step 73). Next, the processing unit 3 compares the calculated DC components and the average values of the AC components (step 74). In FIG. 4, the average value of the DC component is simply expressed as “DC component”, and the average value of the AC component is simply expressed as “AC component”. When the average value of the alternating current component exceeds the average value of the direct current component as a result of the comparison, the processing unit 3 determines that the type of the line current I and the line voltage U input to the channel CH is alternating current. The channel CH is set for alternating current, and that effect is stored in the storage unit 4 (step 75).

  On the other hand, when the average value of the alternating current component is equal to or less than the average value of the direct current component in step 74, the processing unit 3 determines whether or not the condition that the minimum value is less than zero and the maximum value exceeds zero is satisfied. (Step 76). As a result of this determination, when this condition is satisfied, it is determined that the type of the line current I and the line voltage U input to this channel CH is alternating current, and this channel CH is set for alternating current. Is stored in the storage unit 4 (step 77). On the other hand, if the condition is not satisfied as a result of the determination, the processing unit 3 determines that the type of the line current I and the line voltage U input to the channel CH is DC, and uses the channel CH for DC. And the fact is stored in the storage unit 4 (step 78). The processing unit 3 executes the above-described type setting process 65 for each channel CH to perform setting for AC or DC. Thereby, the type setting process 65 is completed.

  Subsequently, the processing unit 3 executes a synchronous integration setting process 66 as shown in FIG. 3 (step 66). In the synchronous integration setting process 66, as shown in FIG. 5, the processing unit 3 first determines whether or not the channel CH is set for AC (step 81). When calculating the effective value of the electric current, the integrated current, and the effective value of the voltage and the effective value of the voltage, the synchronization is performed at the zero crossing point of the line voltage U set as the synchronization original signal in step 63. Then, the power, integrated current, and integrated power integration method are set to AC integration (step 83). On the other hand, when the channel CH is set for direct current in step 81, the channel CH is set so as to be synchronized in a predetermined time (step 84), and then power, integrated current, and integrated power integration method Is set to DC integration (step 85). The processing unit 3 executes the above-described synchronization integration setting process 66 for each channel CH, and executes setting of synchronization and calculation of power, integration current, and integration power. Thereby, the synchronous integration setting process 66 is completed.

  Subsequently, the processing unit 3 executes a harmonic setting process 67 as shown in FIG. 3 (step 67). In the harmonic setting process 67, as shown in FIG. 6, the processing unit 3 detects whether or not there is a channel CH set for alternating current when calculating the harmonic component (step 91). If it exists, it is set so as to be synchronized at the zero cross point for the line voltage U of the channel CH set for AC (step 92). When there are a plurality of channels CH set for alternating current, for example, the channel number U is set so as to be synchronized at the zero cross point with respect to the line voltage U of the channel CH having the smallest number. On the other hand, in step 91, when there is no channel CH set for alternating current among the other channels CH, that is, when all the channels CH are channels CH set for direct current, in a predetermined time period. Setting is made so as to be synchronized (step 93). The processing unit 3 executes the above-described harmonic setting process 67 for each channel CH, and executes the synchronization setting when calculating the harmonic component. Thereby, the harmonic setting process 67 is completed.

  As described above, after the setting for the internal items is completed, the processing unit 3 includes data for specifying the operation of the calculation start button in the operation data D2 input from the setting unit 5 as shown in FIG. If the data is included, the power calculation process (step 53) and the harmonic component calculation process (step 54) are executed. In this power calculation process, the processing unit 3 calculates the power for each channel CH in accordance with the setting contents of each internal item set by the manual setting or the simple setting process in step 51. In this harmonic component calculation process, the processing unit 3 calculates a harmonic component for each channel CH in accordance with the setting contents of each internal item set in the manual setting or the simple setting process in step 51.

  Specifically, the processing unit 3 performs the zero crossing of the line voltage U based on the voltage data Du stored in the storage unit 4 for each channel CH set for AC by the synchronous integration setting processing 66. While detecting the point, the voltage data Du and the current data Di are calculated while synchronizing at the zero cross point, that is, in one cycle unit of the zero cross point. Next, power, integrated current, and integrated power are calculated while applying the RMS rectification method to the calculated voltage data Du and current data Di. On the other hand, the processing unit 3 calculates the voltage data Du and the current data Di for each channel CH set for direct current through the synchronous integration setting processing 66 while synchronizing in a certain time. Next, power, integrated current, and integrated power are calculated while applying the RMS rectification method to the calculated voltage data Du and current data Di. The processing unit 3 also calculates the voltage data Du and the current data Di in one cycle unit of the zero cross point when the harmonic component is also set to be synchronized with the zero cross of the line voltage U of an arbitrary channel. Then, a harmonic component is calculated based on the calculated voltage data Du and current data Di. On the other hand, if synchronization is set for a certain time, the voltage data Du and current data Di are calculated in this time unit, and then harmonic components are calculated based on the calculated voltage data Du and current data Di. calculate. In addition, the processing unit 3 causes the display unit 6 to display the power and harmonic components of each channel CH calculated in this way.

  As described above, according to the wattmeter 1, by operating the simple setting button 5a disposed in the setting unit 5, the processing unit 3 can perform internal items necessary for calculating the power and harmonic components of each channel. Because it is possible to automatically determine the setting contents while automatically determining the type of line voltage (AC or DC), a plurality of internal items required for calculating power and harmonic components Compared with a configuration in which the setting is manually performed, the setting can be completed very easily while avoiding an erroneous setting. Therefore, according to this wattmeter 1, regardless of the type of the line voltage, that is, regardless of the type of the measured circuit, the power and the harmonic component of the measured circuit can be easily and automatically measured in a short time. can do.

  In addition, this invention is not limited to said structure. For example, although the above-described configuration for executing calculation of harmonic components together with the calculation of power has been described above, a configuration for executing only calculation of power can also be adopted. In this configuration, the configuration related to the above-described harmonic components is omitted. Can do.

DESCRIPTION OF SYMBOLS 1 Wattmeter 2 Input part 3 Processing part 5 Setting part 5a Simple setting button 66 Synchronous integration setting process CH1-CH4 Channel Di Current data Du Voltage data I Line current U Line voltage

Claims (2)

A set of current detection terminals and voltage detection terminals configured to be able to input the line current and the line voltage of the circuit to be measured one channel at a time are provided for a plurality of channels, and the line current and the line input from each channel are provided. An input unit that samples and converts the voltage between current data and voltage data, and outputs the data,
A setting unit for setting the type of the measured circuit connected to each channel for each channel;
A power meter comprising: a processing unit that executes a power calculation process for calculating power for each channel based on the current data and the voltage data of each channel output from the input unit;
The setting unit is provided with a setting button,
When the setting button is operated, the processing unit sets the channel for which the set type is an AC electric circuit for AC, and the set type is a single-phase two-wire electric circuit. For a channel, a type setting process for setting for AC or DC depending on the type of the line voltage input to the channel, and
The channel set for AC in the type setting process is set to calculate the power in synchronization with the zero cross point of the line voltage input to the channel, and for the DC in the type setting process. A wattmeter that executes a synchronous integration setting process for setting the channel to set the power to be calculated by DC integration every predetermined time.   The processing unit is configured to be able to execute a harmonic component calculation process for calculating a harmonic component for each channel based on the current data and the voltage data of each channel, and the setting button is operated. Sometimes, for the channel set for AC in the type setting process, the harmonic component is calculated in synchronization with the zero cross point of the line voltage input to the channel, and the type setting process The wattmeter according to claim 1, wherein a harmonic setting process is performed to set the harmonic component to be calculated every predetermined time for the channel set for DC.

Images